Sep 23, 2015

Bashing Bugs on SoCs

posted by Dick Selwood

UltraSoC, the SOC debug company I wrote about a few weeks ago is being pretty imaginative in their marketing. Today, they have launched a new whitepaper,  Performance  Monitoring  Using  UltraSoC by drawing attention to Apple's delay in launching watchOS 2. All that is generally known is that the delay was caused "by a bug" which most news channels have assumed was purely a software issue. UltraSoc is speculating that it might have been something within the SoC that caused the problem. The company also draws attention to Samsung's issues with the launch of the S6 phone and Land Rovers issues over doors unlocking.

Certainly any form of debugging of software running on a large complex SoC is fiendishly difficult, so you might want to download the whitepaper yourself from here. And you don't have to register to get it. Well done UltraSoC.

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Sep 22, 2015

Single-Radio Zigbee and Thread

posted by Bryon Moyer

Earlier this year we saw that Zigbee and Thread were collaborating to implement Zigbee profiles or “clusters,” which normally appear at the top of a Zigbee stack, over the Thread stack as well.

Strategically, this allows top-level Zigbee to handle IP-based data, since Thread includes 6LoWPAN, an IPv6 adaptation for running over 802.15.4, the radio protocol used by Zigbee. Much of the world operates with IP on layer 3; this allows Zigbee infrastructure to participate.

That’s at the top of the stack. Meanwhile, at the bottom, Greenpeak recently announced a single-radio implementation of Zigbee and Thread in their GP712. It can handle both flows with a single radio – or, alternatively, it can serve as a single-stack chip, usable for either stack with a single stocking unit. It needs a thin layer to mux/demux the traffic into the appropriate stack once it leaves the radio.

This got me thinking about how these two reconvergent stacks might play together in different devices. This is based on realizing that an Internet of Things (IoT) edge node is likely to implement only one of the two protocols. So a mixed device isn’t likely to serve there (except as a single-SKU chip that goes either way).

Greenpeak says they’re targeting infrastructure nodes – hubs, gateways, set-top boxes and the like – and those devices are indeed likely to be managing multiple traffic streams across multiple platforms. On the other hand, it’s unlikely that they’ll be working at the application layer (except perhaps for deep packet inspection).

It may be a failure of imagination on my part, but the only node I can picture that might realistically process multiple protocols and implement the application layer would be a server. I’d include a phone as a possible server, although phones typically don’t do 802.15.4.

The following figures illustrate the different configurations that I’ve derived from this mental wandering. Presumably, the GP712 could serve in any of them with appropriate configuration.


You can read more about Greenpeak's new device in their announcement.

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Sep 15, 2015

Designing Irregular Light

posted by Bryon Moyer

Light_image.pngSynopsys recently announced their latest update to their LightTools optical design suite, which we’ve looked at before. The… um… focus (sorry) of this release appears to be on irregular light patterns and behavior.

Any of us who dissected a flashlight as a kid likely understands that the light beam is round because the the “lens” (that cheap piece of flat plastic) is round that reflector thingy in the back is round.

So what if you want something that’s not round? What if you want something irregular, even organic? Tools have been able to handle that, but they require that you set up thousands of parameters to get it to work.

What Synopsys has done with this release is allow users to abstract those parameters to a few higher-level ones, like specifying the light source and the desired illumination pattern. The latter, of course, if it’s a complicated shape, can still be complex to define, but apparently it’s far easier – and more intuitive – than what has been required to date.

Because you can specify any shape under the sun, these are referred to as “freeform optics.” The lenses can end up with some strange shapes, but the good news is that the tools calculate the shapes from the specified higher-level characteristics.

The lenses and reflectors we’re mostly used to are smooth and continuous. But that’s not been the case for a particular class of light, originating with headlamps on cars. Their design challenge is to create a bright spot on the road and illuminate signs and other features – and wild animals – without blinding oncoming traffic.

So faceted reflectors have been used in this application. Instead of being continuously curved, you can think of these reflectors as being piecewise curved: except at the facet transitions, each point is on a flat surface. The shapes, angles, and positioning of the facets are what determine where the light goes.

So the driver’s side headlamp cuts off the top of the beam to limit how much it hits an oncoming driver. The passenger side light, however, is allowed to shine higher since there are no oncoming drivers on that side, while there are street signs. Such lights are also used for streetlights and architectural lighting, both situations where you might want to control the placement of light.

The latest LightTools release allows designers to specify the desired light spread for different facets and have the tool design the reflector.

Meanwhile, it turns out that phosphors used in LEDs have temperature-dependent properties. The latest LightTools now models that behavior so that lighting can be designed to deliver as promised across temperature.

And finally, while many common materials have scattering properties that LightTools understands already, they’ve now added the ability to specify custom scattering – useful for new, proprietary materials. The custom scattering algorithm is compiled into a DLL, so performance is not significantly diminished from scattering algorithms that the tool supports natively.

You can find more in their announcement.


(Image courtesy Synopsys)

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